Methods for controlling a flow pulse shape

ABSTRACT

Methods for controlling pulse shape in ALD processes improves local non-uniformity issues of films deposited on substrate surface. The methods include using a variable flow valve creating predetermined pulse shape when a reactant is provided on a substrate surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No.62/902,918, filed Sep. 19, 2019, the entire disclosure of which ishereby incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to methods for controlling pulse shape inALD processes. In particular, embodiments of the disclosure relate togenerating predetermined flow pulse profile using a variable flow valve.

BACKGROUND

Atomic layer deposition typically involves reacting alternating pulsesof two or more reactants to deposit film layers on a substrate surfacein a reaction chamber. The pulse is generally formed when a valve isopened. FIG. 1 illustrates a schematic of a common gas delivery system10. An ampoule 12 is connected through gas lines 11 to a mass flowcontroller 14, a downstream reservoir 15, an atomic layer deposition(ALD) valve 17 into the process chamber 19.

A square wave pulse, see FIG. 2A is intended by the opening and closingof the ALD valve 17. However, upon opening the ALD valve 17, a drop inpressure results in a pulse shape resembling FIG. 2B. The pulse willhave a shape that includes a rising transition at the start, a fallingtransition at the end, and potentially a trend in the middle if the flowthrough the valve isn't constant during the duration of the pulse.Additionally, the transitions of ALD valve 17 from closed to open, andvice versa, should be fast to minimize the rising and fallingtransitions, and the shape of the pulse should match from pulse topulse.

One disadvantage of the current state of art is that the pulses are ofshort duration. In the absence of any pulse controlling system,different parts of the substrate surface in the reaction chamber willsee the pulses at different times and of different dose, creatinglocalized non-uniformity issues. For example, FIG. 3 illustrates aportion of a typical reaction chamber where the gases are delivered froma showerhead 20, or other gas injector, above the substrate 30 and flowout radially towards a pump. The center of the substrate 30 surface willsee the pulse before the edge and will also see the pulse removed beforethe edge. Moreover, the flow rate of the gas, indicated by arrows 25,accelerate as the gas moves from the center of the wafer to the edge,resulting in non-uniform precursor dosing across the wafer surface.

Therefore, there is a need in the art for methods for controlling pulseshape in ALD processes to improve uniformity.

SUMMARY

One or more embodiments of the disclosure are directed to processingmethod comprising flowing a gas through a variable flow valve to asubstrate support. The variable flow valve is controlled to generate apredetermined flow pulse profile to the inner region and outer region ofthe substrate support.

Additional embodiments of the disclosure are directed to gas deliverysystems comprising: a gas reservoir having a charged pressure; avariable flow valve; and a controller configured to control the variableflow valve to generate a predetermined flow pulse profile downstream ofthe variable flow valve.

Further embodiments of the disclosure are directed to non-transitorycomputer readable medium including instructions, that, when executed bya controller of a processing chamber, causes the processing chamber tocontrol a variable flow valve to generate a predetermined flow pulseprofile to an inner region and an outer region of a substrate support.

BRIEF DESCRIPTION OF THE DRAWING

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments. The embodiments as described herein areillustrated by way of example and not limitation in the figures of theaccompanying drawings in which like references indicate similarelements.

FIG. 1 illustrates a schematic representation of a prior art gasdelivery system;

FIG. 2A illustrates a square wave pulse shape;

FIG. 2B illustrates a typical pulse shape from a system according toFIG. 1 ;

FIG. 3 illustrates a schematic representation of gas flows in a processchamber at the substrate surface;

FIG. 4 illustrates a process flow diagram of a method according to oneor more embodiments;

FIG. 5 illustrates a schematic representation of the method according toone or more embodiment; and

FIG. 6 illustrates representative pulse shapes for reactants that can beconfigured using one or more embodiment of the disclosure.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the invention, it isto be understood that the invention is not limited to the details ofconstruction or process steps set forth in the following description.The invention is capable of other embodiments and of being practiced orbeing carried out in various ways.

A “substrate” as used herein, refers to any substrate or materialsurface formed on a substrate upon which film processing is performedduring a fabrication process. For example, a substrate surface on whichprocessing can be performed include materials such as silicon, siliconoxide, silicon dioxide, strained silicon, silicon on insulator (SOI),carbon doped silicon oxides, amorphous silicon, doped silicon, and anyother materials such as metals, metal nitrides, metal alloys, and otherconductive materials including aluminum oxide, depending on theapplication. In addition to film processing directly on the surface ofthe substrate itself, in the present disclosure, any of the filmprocessing steps disclosed may also be performed on an underlayer formedon the substrate as disclosed in more detail below, and the term“substrate surface” is intended to include such underlayer as thecontext indicates. Thus for example, where a film/layer or partialfilm/layer has been deposited onto a substrate surface, the exposedsurface of the newly deposited film/layer becomes the substrate surface.

As used in this specification and the appended claims, the terms“precursor”, “reactant”, “reactive gas” and the like are usedinterchangeably to refer to any gaseous species that can react with thesubstrate surface.

One or more embodiments of the disclosure are directed to methods forcontrolling the shape of the gas pulse injected into a processingchamber. In some embodiments, the pulse shape is controlled using avalve with variable flow during the pulse in order to create differentpulse profiles on the wafer. In some embodiments, the variable flowvalve has a variable opening size which can be changed during the pulse.

Some embodiments advantageously provide the ability to match one or moreof the concentration, dose or residence time at different portions ofthe wafer surface. Some embodiments advantageously provide smoothertransitions between two gases. Some embodiments are used withback-to-back plasma processes with improved dose control. Someembodiments create controlled disturbances in the gas flow for localnon-uniformity improvement.

FIG. 4 illustrates a schematic representation of a gas delivery system100 according to one or more embodiment of the disclosure. The gasdelivery system 100 illustrated comprises a gas source gas 110. The gassource can be any suitable gas source including, but not limited to,precursor ampoules and house gas lines.

The gas source 110 is in fluid communication with a gas reservoir 120located downstream of the gas source 110. The terms “upstream” and“downstream” are used to describe the position of components relative tothe direction of flow of gas. The direction of flow is from the gassource 110 to the processing chamber 140.

In some embodiments, a valve (not shown) is positioned between the gassource 110 and the gas reservoir 120. In some embodiments, the valveallows for the removal and/or replacement of the gas source 110. In someembodiments, the valve allows the system to charge the gas reservoir 120to a predetermined pressure by opening and closing at predeterminedintervals to maintain a predetermined pressure.

The gas reservoir 120 is down stream of the gas source 110 and maintainsa supply of gas. The gas reservoir is charged from the gas source 110 toa predetermined pressure, referred to as the charged pressure. Thecharged pressure is the target pressure in the reservoir, which may ormay not be the maximum pressure rating for the reservoir. In someembodiments, the charged pressure is less than or equal to 98%, 95%,90%, 80%, 70%, 60%, 50%, 40%, 30%, 20% or 10% of the maximum pressurerating for the reservoir.

The gas reservoir 120 of some embodiments includes a sufficient pressureand/or volume to prevent large fluctuations during draw periods. Forexample, when the variable flow valve 130, located downstream of the gasreservoir, is opened, the flow does not change the pressure and/orvolume of gas in the reservoir by greater than or equal to 10%, 8%, 6%,4%, 2% or 1% relative to the charged pressure and/or volume.

The variable flow valve of some embodiments is a fast acting valve thathas a short full actuation time. In some embodiments, the variable flowvalve has a full actuation time less than or equal to 30 milliseconds(msec). In some embodiments, the variable flow valve has a fullactuation time less than or equal to 25 milliseconds, 20 milliseconds,15 milliseconds or 10 milliseconds. In some embodiments, the variableflow valve has a full actuation time in the range of 5 milliseconds to25 milliseconds, or in the range of 10 milliseconds to 20 milliseconds.

Referring to the pulse illustrated in FIGS. 2A and 2B, the threeportions of the pulse profile 50 are the rising transition 52, theintermediate transition phase 54 and the falling transition 56. In oneor more embodiments, the flow pulse profile 50 includes a risingtransition 52. During the rising transition 52 phase, the variable flowvalve is moved from a closed position in which no flow occurs to an openposition for the predetermined initial flow. For example, the variableflow valve initially closed takes time to move to the predetermined openposition. The portion of the flow pulse profile 50 from the start of thevalve opening to the predetermined open position is defined as therising transition 52. The predetermined open position can be anysuitable position depending on, for example, the size of the variableflow valve, the flow rate through the valve and/or the dose to bedelivered. In some embodiments, the rising transition 52 phase resultsin the variable flow valve being fully open, partially open,progressively opening fully, and progressively opening partially.

In one or more embodiments, the predetermined flow pulse profileincludes a falling transition phase 56. The falling transition phase 56may result in one or more of the variable flow valve closing fully,closing partially, progressively closing fully, and progressivelyclosing partially. The falling transition phase 56 is measured as thetime period from the point at which the variable flow valve 130 beginsto fully close and is fully closed.

In one or more embodiments, the predetermined flow pulse profileincludes an intermediate transition phase 54. The intermediatetransition phase 54 is the time period between the rising transitionphase 52 and the falling transition phase 56. The intermediatetransition phase 54 of some embodiments results in one or more of thevariable flow valve opening fully, opening partially, progressivelyopening fully, progressively opening partially, closing partially,progressively closing partially, maintaining partial open state, ormaintaining full open state.

In one or more embodiments, one or more of an input and an output of thevariable flow valve has one or more variable openings. In someembodiments, the variable opening is configured to change during theoperation of the flow valve. In one or more embodiments, the variableflow valve has a pressure sensor (not shown). In some embodiments, thevariable opening is configured to change the size of the opening as afunction of one or more of time and pressure. In some embodiments, thevariable flow valve also comprises directing the flow of gas to multiplesubstrate supports at the same time.

FIG. 5 illustrates a flowchart of an embodiment of the method 200according to one or more embodiment of the disclosure. In one or moreembodiments, the variable flow valve 130 is configured to provide a flowpulse profile from a pulse start to a pulse end with a pulse maximumflow at the pulse start and tapering to a pulse minimum flow at thepulse end. In some embodiments, before the pulse start and after thepulse end, there is no flow through the variable flow valve. In someembodiments, the flow pulse profile has a linear taper from the pulsemaximum flow to the pulse minimum flow. In one or more embodiments, theflow pulse profile has a non-linear taper from the pulse maximum flow tothe pulse minimum flow.

In one or more embodiments, the variable flow valve comprises a firstinput, a second input and a controller configured to control the openingof the first input and the second input in a predetermined order. Insome embodiments, the variable flow valve may optionally have a thirdinput connected to an inert gas supply valve. In some embodiments, theinert gas supply valve is connected to N₂, Ar, He, Ne or Kr gasreservoir. In some embodiments, the variable flow valve may have acleansing vent. In some embodiments, the cleansing vent is connected toa vacuum. In some embodiments, each inputs, the first input and thesecond input, has a variable opening. In some embodiments, the variableopening is configured to change the size of the opening duringfunctioning of the variable flow valve. In some embodiments, thevariable opening is configured to change the size of the opening as afunction of one or more of time and pressure.

Downstream of the variable flow valve 130 is the processing chamber 140.The processing chamber 140 can be any suitable chamber includingsemiconductor manufacturing chambers and low-pressure chambers used innon-semiconductor processing. In some embodiments, the processingchamber 140 comprises an atomic layer deposition (ALD) or chemical vapordeposition (CVD) processing chamber. In general, the ALD and/or CVDchamber comprises a chamber body 141 enclosing an interior volume 142. Agas injector 143 (which may also be referred to as a showerhead) is influid communication with the variable flow valve 130 to provide a flowof gas into the interior volume 142. The processing chamber 140 includesa substrate support 144 to hold a substrate during processing.

In one or more embodiments, the flow pulse profile 300 generates auniform dosage across both the inner region 32 and outer region 34 ofthe substrate 30. According to one or more embodiment, method 200 beginswith a reactant 210 stored in a reservoir 120. The method step 220 isperformed by providing the reactant through a variable flow valve 130 toa reaction chamber 140. In some embodiments the variable flow valve 130has a variable opening configured to change size during the functioningof the variable flow valve. For the method step 230, the reactant pulseis provided to the processing chamber 140 with the predetermined pulseshape 300.

In some embodiments, the variable flow valve 130 is connected to atleast one controller 190. In some embodiments, the controller 190 isconfigured to operate the variable flow valve 130 to form thepredetermined pulse shape 300. In some embodiments, the size of theopening in the variable flow valve 130 varies as a function of time. Insome embodiments, the opening in the variable flow valve 130 is variedas a result of pressure changes in the reservoir.

The at least one controller 190 of some embodiments has a processor 192,a memory 194 coupled to the processor 192, input/output devices 196coupled to the processor 192, and support circuits 198 to communicationbetween the different electronic components. The memory 194 can includeone or more of transitory memory (e.g., random access memory) andnon-transitory memory (e.g., storage).

The memory 194, or computer-readable medium, of the processor may be oneor more of readily available memory such as random access memory (RAM),read-only memory (ROM), floppy disk, hard disk, or any other form ofdigital storage, local or remote. The memory 194 can retain aninstruction set that is operable by the processor 192 to controlparameters and components of the system. The support circuits 198 arecoupled to the processor 192 for supporting the processor in aconventional manner. Circuits may include, for example, cache, powersupplies, clock circuits, input/output circuitry, subsystems, and thelike.

Processes may generally be stored in the memory as a software routinethat, when executed by the processor, causes the process chamber toperform processes of the present disclosure. The software routine mayalso be stored and/or executed by a second processor (not shown) that isremotely located from the hardware being controlled by the processor.Some or all of the method of the present disclosure may also beperformed in hardware. As such, the process may be implemented insoftware and executed using a computer system, in hardware as, e.g., anapplication specific integrated circuit or other type of hardwareimplementation, or as a combination of software and hardware. Thesoftware routine, when executed by the processor, transforms the generalpurpose computer into a specific purpose computer (controller) thatcontrols the chamber operation such that the processes are performed.

In some embodiments, the controller 190 has one or more configurationsto execute individual processes or sub-processes to perform the method.The controller 190 can be connected to and configured to operateintermediate components to perform the functions of the methods. Forexample, the controller 190 can be connected to and configured tocontrol one or more of gas valves, actuators, motors, slit valves,vacuum control, pressure gauges, etc.

The controller 190 of some embodiments has one or more configurationsselected from: a configuration to control the rising transition phase 52of a pulse through a variable flow valve 130; a configuration to controlthe intermediate transition phase 54 of a pulse through the variableflow valve 130; a configuration to control the falling transition phase56 of a pulse through a variable flow valve 130; a configuration tomeasure pressure in a pressure reservoir 120; and/or a configuration tocharge a pressure reservoir 120.

Referring to FIG. 6 , the pulse shape 300 can be controlled to create amore uniform precursor dose across the inner region and outer regions ofthe substrate. Pulse profiles can be generated with linear intermediatetransition phases 54, like pulses 301 and 305. In some embodiments, thepulse profile has no intermediate transition phases 54, like pulses 302and 303. In some embodiments, the pulse profile has a non-linerintermediate transition phase 54 like pulses 306-309. In someembodiments, the pulse profile is stepped, like pulse 310. The skilledartisan will recognize that the pulse profiles 300 illustrated in FIG. 6are merely representative of possible pulse profiles and that theindividual profile used may depend on, for example, the gas injector,the substrate to gas injector spacing, the flow rates, the reservoirsize/pressure, etc.

In one or more embodiments, a gas delivery system comprises a gasreservoir having a charged pressure, a variable flow valve, and acontroller configured to control the variable flow valve to generate apredetermined flow pulse profile downstream of the variable flow valve.In some embodiments, the variable flow valve is downstream of and influid communication with the gas reservoir. In some embodiments, thevariable flow valve is upstream of and in fluid communication with thegas reservoir. In some embodiments, the variable flow valve comprisesone or more of a variable input and a variable output having a variableopening. In some embodiments, the size of opening changes as a functionof one or more of a time and a pressure.

In one or more embodiments, the gas delivery system is connected to oneprocessing chamber. In some embodiments, the gas delivery system isconnected to multiple process chambers at the same time. In amulti-chamber system, the gas line splits upstream of the variable flowvalve 130 into multiple gas legs, each leg having a separate variableflow valve 130.

In some embodiments, there are multiple reservoirs upstream of thevariable flow valve. In some embodiments, the variable flow valve hasmultiple inputs connected to the multiple reservoirs. In someembodiments, the variable flow valve has multiple outputs, each outputconnected to a different processing chamber.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, those skilled in the art will understand thatthe embodiments described are merely illustrative of the principles andapplications of the present disclosure. It will be apparent to thoseskilled in the art that various modifications and variations can be madeto the method and apparatus of the present disclosure without departingfrom the spirit and scope of the disclosure. Thus, the presentdisclosure can include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A processing method comprising: flowing a gasthrough a variable flow valve to a substrate support; and controllingthe variable flow valve to generate a predetermined flow pulse profileto the inner region and outer region of the substrate support, whereinthe variable flow valve is configured to provide a flow pulse profilefrom a pulse start to a pulse end with a pulse maximum flow at the pulsestart and tapering to a pulse minimum flow at the pulse end.
 2. Theprocessing method of claim 1, wherein the flow pulse profile has arising transition phase comprising one or more of the variable flowvalve opening fully, opening partially, progressively opening fully, andprogressively opening partially.
 3. The processing method of claim 2,wherein the flow pulse profile has a falling transition phase comprisingone or more of the variable flow valve closing fully, closing partially,progressively closing fully, and progressively closing partially.
 4. Theprocessing method of claim 3, wherein the flow pulse profile has anintermediate transition phase, wherein the intermediate transition phaseoccurs between the rising transition phase and the falling transitionphase.
 5. The processing method of claim 4, wherein the intermediatetransition phase comprises one or more of the variable flow valveopening fully, opening partially, progressively opening fully,progressively opening partially, closing partially, progressivelyclosing partially, maintaining partial open state, and maintaining fullopen state.
 6. The processing method of claim 1, wherein one or more ofan input and an output of the variable flow valve comprises a variableopening.
 7. The processing method of claim 6 further comprises directingthe flow of gas to multiple substrate supports at the same time.
 8. Theprocessing method of claim 6, wherein the variable flow valve has morethan one output.
 9. The processing method of claim 1, wherein thevariable flow valve has a pressure sensor.
 10. The processing method ofclaim 1, there is no flow through the variable flow valve before thepulse start and after the pulse end.
 11. The processing method of claim1, wherein the flow pulse profile has a linear taper from the pulsemaximum flow to the pulse minimum flow.
 12. The processing method ofclaim 1, wherein the flow pulse profile has a non-linear taper from thepulse maximum flow to the pulse minimum flow.
 13. The processing methodof claim 1, wherein the flow pulse profile generates a uniform dosageacross both the inner region and outer region of the substrate support.